With the increasing need of service availability for provider networks, protection techniques (also known as Fast ReRoute—FRR) are becoming increasingly important. Unfortunately, Internet Protocol (IP) networks do not provide fast reroute capability other than multi-protocol label switching (MPLS) FRR managed with resource reservation protocol (RSVP). Since building and keeping up MPLS tunnels using RSVP scales poorly in large networks, alternative solutions are needed. Techniques providing protection in pure IP or label distribution protocol (LDP)-MPLS networks are known as IP Fast ReRoute (IPFRR) techniques. Unfortunately, since IP (and LDP) forwards packets to a given destination always following the shortest path, i.e., a path through the network determined using the shortest path first (SPF) algorithm, fast reroute for these networks is difficult.
Only one IPFRR technique, Loop-Free Alternates (LFA), has been implemented by vendors of networking devices. Unfortunately, LFA is a simplest IPFRR method, which cannot cover all the possible failure scenarios. This disadvantage is so serious, many networking device vendors and operators work around the limitations of LFA trying to improve IPFRR failure coverage by organizing the topology of the networks being built to become “LFA friendly” (e.g., Seamless MPLS). Naturally, this results in significant extra expenditure in additional links and networking devices when a network is built, but there is an even more important problem: no matter how carefully a network is designed, a failure immediately ruins its topology, and after the recovery process it is impossible to provide 100% failure coverage since the designed topology is lost. Any network of sufficient size will always contains failed parts, i.e., failed links or nodes, therefore full failure coverage cannot be provided in this way.